These objects are achieved, for example, by providing the circuit breaker with a pair of additional contacts capable of generating a secondary arc during circuit breaker opening.
For example, a circuit breaker of this type is described in published German patent application No. 2 349 263.
A drawback of the prior art circuit breaker is the increase in the weight of the moving equipment due to the presence of one of the secondary contacts. This increase in weight means that the circuit breaker must be provided with a more powerful control mechanism, thereby increasing the cost of the apparatus.
An object of the invention is to provide a circuit breaker having secondary contacts, but in which the weight of the moving equipment is not increased.
Another object of the invention is to provide a circuit breaker which is compact, and therefore cheap to build and having low maintenance costs.
Document DE-A-2 403 300 describes a circuit breaker provided with secondary contacts. One of them, the secondary contact farther from the blast nozzle, is fixed to the moving equipment, while the other one of them is semi-moving relative to the fixed equipment. Such a circuit breaker suffers from a drawback: the length of the secondary arc is not necessary limited; as a result, the arc may lengthen excessively during a circuit breaker opening operation, thereby overheating the surrounding gas; such overheating may prevent the circuit breaker from performing a rapid open-close-open (OCO) cycle since the gas does not have time to cool down sufficiently after the first open; consequently the medium remains highly ionized and the second open operation may fail since the secondary arc does not extinguish during the current zero crossing.
Another drawback of excessively lengthening the arc is that the arc may damage the parts surrounding it.
An additional object of the present invention is to provide a circuit breaker which does not have the above-mentioned drawbacks.